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SN6507: High heat when current limitation is applied

user5397266
Prodigy 230 points
Part Number: SN6507

Hi team,

Why does the SN6507 get hotter when current limiting is applied?

The same load will be much hotter when current limiting is applied than when the threshold is set higher to avoid current limiting.

Also, please tell me how to prevent it from generating heat.

Thank you

  • 0
    TI__Guru 53095 points

    Hi,

    Thank you for reaching out.

    Please note that when device hits the current limit threshold that is set using RILIM resistor, it operates in hiccup mode until current reduces to a value below the threshold limit. Due to this hiccup mode of operation, it is possible that the device heats up more than normal due to frequent switching ON/OFF the MOSFETs and increasing switching losses.

    I would also like to mention that the device should not be operated in current limit, as it is not expected to operate normal. Please set the current limit such that the limit is not hit under normal operating conditions and it only hits if the current exceeds normal operating conditions for your application. Let me know if you have any questions, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 230 points

    Hi,

    Naturally, the RILIM is not current-limited during normal use.

    The problem is when a transformer fails due to a short circuit.

    If one of the output windings short-circuits, the SN6507 current limit will be applied and the temperature will rise to over 150°C, but the load will not be high enough to blow the fuse.

    Therefore, countermeasures against heat generation are necessary, but is it possible to implement the countermeasures in the IC itself?

    Thank you

  • 0 in reply to user5397266
    TI__Guru 53095 points

    Hi,

    Thank you for sharing additional information.

    user5397266 said:
    Naturally, the RILIM is not current-limited during normal use.

    Understood.

    user5397266 said:
    If one of the output windings short-circuits, the SN6507 current limit will be applied and the temperature will rise to over 150°C, but the load will not be high enough to blow the fuse.

    Yes, this is expected. As I mentioned in my previous response, the device switches much faster than the set switching frequency causing higher switching losses and heating up device. This is expected behavior and measures should be taken to detect overcurrent condition and remove the condition or turn off the device.

    user5397266 said:
    Therefore, countermeasures against heat generation are necessary, but is it possible to implement the countermeasures in the IC itself?

    There are no countermeasures possible to be implemented in device, this has to be addressed externally.

    Let me know if you have any other questions. If there are no further questions then I will go ahead and mark this post as closed. Thanks.


    Regards,
    Koteshwar Rao